1. Field of the Invention
The present invention relates to an ink jet recording ink which can yield a print having high quality with high reliability on various recording media, especially on plain papers, recycled papers, and special papers having thereon an ink-receptive layer.
2. Background Art
Ink jet recording is a method wherein an ink is ejected as a droplet through a fine nozzle to record letters or figures onto the surface of a recording medium. Ink jet recording systems which have been put to practical use include: a method wherein an electric signal is converted to a mechanical signal using an electrostrictive strain to intermittently eject an ink reservoired in a nozzle head section, thereby recording letters or symbols on the surface of a recording medium and a method wherein an ink, reservoired in a nozzle head section, in its portion very close to the ejection portion is rapidly heated to create a bubble and the ink is intermittently ejected by volume expansion created by the bubble to record letters or symbols on the surface of a recording medium.
Properties required of inks used in the ink jet recording includes a good drying property of the print, no feathering created, homogeneous printing performed on the surface of various recording medium, and, in the case of multi-color printing, no color-to-color intermixing occurred.
Feathering on paper occurs attributable to the presence of fibers different from each other in ink penetration, a black ink and a color ink are intermixed at the boundary therebetween to deteriorate the image quality. Further, when the ink put on a recording medium is touched with a hand, the ink is unfavorably detached from the recording medium.
In order to overcome these drawbacks, various ink compositions have been proposed in the art.
For example, Japanese Patent Publication 2907/1990 proposes an ink containing glycol ether as a wetting agent, Japanese Patent Publication 15542/1989 proposes an ink containing a water-soluble organic solvent, and Japanese Patent Publication 3837/1990 proposes an ink containing a dye solubilizer.
Further, in order to improve the penetrability of the ink, U.S. Pat. No. 5,156,675 proposes addition of diethylene glycol monobutyl ether, U.S. Pat. No. 5,183,502 proposes addition of Surfynol 465, an acetylene glycol surfactant, and U.S. Pat. No. 5,196,056 discloses addition of both diethylene glycol monobutyl ether and Surfynol 465. Diethylene glycol mono-n-butyl ether is known also as butylcarbitol and described, for example, in U.S. Pat. No. 3,291,580. Further, utilization of an ether of diethylene glycol has been studied in U.S. Pat. No. 2,083,372. Furthermore, Japanese Patent Laid-Open No. 147861/1981 proposes use of a pigment and triethylene glycol monomethyl ether in combination.
Despite the proposal of the various inks, an ink composition capable of realizing an image having no significant feathering and bleeding has been still desired in the art.
Further, heating recording paper has been studied in order to reduce feathering and bleeding. Heating of the recording paper at the time of recording, however, poses problems including that a lot of time is taken for building up the heating section in the apparatus to a predetermined temperature, power consumption of the body of the apparatus is increased, or recording paper or other recording media are damaged by the heat.
In the ink composition using a pigment, an attempt to suppress penetration of the ink in the surface of a recording medium has been made to ensure the print quality. In some cases, however, when the ink composition does not penetrate into the recording medium to a certain extent, the pigment is left on the surface of the recording medium, deteriorating the scratch resistance of the print. Further, in recent years, a recording medium has been utilized wherein a gloss layer is provided thereon, a gloss is put on the recorded image and added value is imparted to the image. A pigment-type ink capable of realizing an image having good scratch resistance on the recording medium has been desired in the art.
The present inventors have now found that an ink composition comprising a combination of a particular pigment with an acetylene glycol surfactant can effectively suppress feathering or bleeding and can realize a high-quality image having excellent scratch resistance. The present invention has been made based on this finding.
Accordingly, an object of the present invention is to provide an ink composition which can realize a good image having no significant feathering or bleeding on various recording media, especially on plain paper, recycled paper, and recording media having thereon a gloss layer.
According to the present invention, there is provided an ink composition comprising a pigment, a water-soluble organic solvent, a surfactant, and water, wherein the pigment is dispersible and/or soluble in water without a dispersant and the surfactant is an acetylene glycol surfactant.